1. Field of the Invention
The present invention relates to stretching and compressing electromagnetic pulses, and more particularly laser pulses.
2. Description of Related Art
Chirped pulse amplification (CPA) is very useful for producing ultrashort-duration high-intensity pulses for use in high peak power ultrashort pulse laser systems. CPA increases the energy of an ultrashort laser pulse while avoiding optical amplifier damage. In this technique, the duration of the pulse is increased by first dispersing the ultrashort laser pulse temporally as a function of wavelength (a process called “chirping”) to produce a chirped pulse, then amplifying the chirped pulse, and then recompressing the chirped pulse to significantly shorten its duration. Lengthening the pulse in time reduces the peak power of the pulse and, thus, allows energy to be added to the pulse without reaching a damage threshold of the pulse amplifier and optical components. The amount of pulse amplification that can be achieved is typically proportional to the amount of pulse stretching and compression. Typically, the greater the amount of stretching and compression, the greater the possible pulse amplification.
A fiber Bragg grating may be used for chirping a pulse and recompressing the pulse. However, the amount of stretching or compression by the fiber Bragg grating is substantially fixed by the physical dimensions of the fiber Bragg grating. Thus, various sizes of fiber Bragg gratings are used for chirping and/or compressing pulses. In some fiber Bragg gratings, nominal adjustments to the pulse length may be provided by physically, mechanically, or thermally stretching the optical fiber of the fiber Bragg grating to modify the length of the optical fiber. Unfortunately, the amount of adjustment to the pulse length is relatively small and the optical fiber may suffer damage from the physical stress and strain of the stretching. There is, therefore, a need for improved systems and methods of stretching and compressing optical pulses.